Inter-base station carrier aggregation (CA) is introduced in the Long Term Evolution (LTE) release (Rel)-12. In a dual connectivity (DC) communication scenario related to the inter-base station carrier aggregation, UE is connected to two base stations to transmit and receive data. Because there is non-ideal backhaul (Backhaul) and a specific scheduling delay between the base stations, the base stations cannot exchange scheduling information of the UE in real time. The two base stations may be a master base station and a secondary base station, and may separately include one or more cells. A carrier group or a cell group of the master base station is referred to as a master carrier group or a master cell group (MCG), and a carrier group or a cell group of the secondary base station is referred to as a secondary carrier group or a secondary cell group (SCG). In a DC system, two base stations are not required to be synchronous. That is, any time difference exists at start moments of downlink transmit subframes of the two base stations, and the downlink transmit subframe plus a timing advance (TA) is an uplink subframe for sending data by corresponding user equipment (UE). Therefore, in a non-synchronous DC scenario, time may mutually overlap in uplink subframes sent by the UE to the two base stations. For example, referring to FIG. 1, a cell 1 and a cell 2 separately pertain to cell groups (or carrier groups) of different base stations. A subframe i is an uplink subframe in the cell 1, a subframe j is an uplink subframe in the cell 2, and the subframe i overlaps with both the subframe j and a subframe j+1 (the subframe j+1 is a next subframe of the subframe j).
When an uplink subframe of the UE in the cell 1 overlaps with an uplink subframe in another different cell, a sum of channel power of the UE in all subframes (the subframe i, the subframe j, and the subframe j+1) in an overlapping part cannot exceed maximum transmit power allowed by the UE. Therefore, when channel power for sending information in the subframe i is being determined, a channel power status of two subframes (the subframe j and the subframe j+1) in a cell in another cell group that overlap with the subframe i needs to be considered.
When the UE does not support “look ahead”, that is, when a processing capability of the UE does not support calculating a channel power status of the future subframe j+1 when the channel power of the subframe i is being determined, because a downlink subframe corresponding to the subframe j arrives at the UE earlier than a downlink subframe corresponding to the subframe i, channel power of the subframe j is known to the UE. A practice in the prior art is as follows.
If the UE may perform uplink channel transmission in a subframe j+1 in a cell group 1 of a base station 1, the UE reserves specific guaranteed power for uplink transmission between the UE and the base station 1. If the UE determines that the UE does not perform uplink channel transmission in the subframe j+1 in a cell group 1, for example, it may be determined, according to semi-static configuration information, that uplink transmission is not performed in the subframe j+1, the UE does not reserve power for uplink transmission of the cell group 1. After the UE reserves the specific guaranteed power for uplink transmission between the UE and the base station 1, the UE may send information in the subframe i by using all remaining power (the remaining power is a difference obtained by subtracting the channel power of the subframe j and the guaranteed power of the subframe j+1 from the maximum transmit power allowed by the UE). That is, in the prior art, an uplink subframe sent first preferably occupies power, and an uplink subframe sent later may use at least guaranteed power of a base station in the uplink subframe.
However, in the prior art, because the two base stations cannot coordinate scheduling of the UE in a timely manner, transmit power of the UE cannot be properly used, for example, a base station that schedules the uplink subframe sent later does not know a scheduling status of the uplink subframe sent first. To ensure that total transmit power of the UE does not exceed the maximum transmit power allowed by the UE, the base station that schedules the uplink subframe sent later schedules the UE according to guaranteed power of the base station in the foregoing scheduling policy. However, if the UE is not scheduled in the uplink subframe sent first or is scheduled to use less channel power, the power of the UE is wasted and cannot be used for uplink transmission in the uplink subframe sent later. In another case, a scheduling policy of the base station that schedules the uplink subframe sent later is relatively radical, and the UE is scheduled by using power exceeding the guaranteed power of the base station. However, channel power used for scheduling the UE in the uplink subframe sent first is also quite high. Consequently, the total transmit power of the UE may exceed the maximum transmit power allowed by the UE, power in the uplink subframe sent later is compressed, and a bit error rate increases.